The present invention relates to devices for recording changes in pneumatic pressure, such as, for example, those encountered during measurement of blood pressure.
Thus, the present invention is particularly concerned with a device for recording values of pressure, in particular blood pressure, especially as derived from the use of a sphygmomanometer according to the Riva-Rocci/Korotkoff method.
With the invention a connection is made to the cuff of a sphygmomanometer in order to derive therefrom a pneumatic pressure which is then converted into a corresponding mechanical motion, the operation, being brought about in response to an electrical signal which initiates the operation of the recording device.
There are already known methods and devices for recording specific blood pressure values according to such methods, namely the systolic and/or diastolic pressure.
However, the known methods and devices require improvement. Thus, experience has shown that the known devices are of an extremely expensive construction so that, in spite of the importance of the information, when taking into consideration the purpose thereof, nevertheless the known constructions are too costly. The costs involved for both electronic and mechanical structures of the known devices is extremely high, inasmuch as it is not possible to provide known devices of this type without a special pressure transducer as well as an electronic amplifier, while on the other hand, the power supply components must be stabilized and several such components are required.
In connection with only the use of a recording device, it is required to have a complete drive for the paper strip which receives the recorded information, including a driving motor as well as transmission components, elements for guiding the paper strip, bearing components for the paper roll and the like. The large number of components required for this type of recorder results, however, in a relatively great loss of reliability in the operation.
Moreover, since, on the other hand, there are on the market a number of older blood pressure measuring devices including, for example, microphones, sphygmomanometer cuffs, and a simple device for introducing air under pressure into the cuff, there is also a need to complete such devices in a manner making it possible for them to be used for recording blood pressure, but up to the present time this requirement has not been satisfied.
Of considerable importance in this connection is also the fact that the sheet material used for recording information up to the present time is in the form of a paper recording strip providing only a limited accuracy in the reading of the values, such as is possible, for example, with a recording strip which has a width of 60 mm with graduations of 300 mm Hg pressure. At the same time, these units have the disadvantage of limiting a given body of information only to a part of the entire strip which also contains data in connection with other tests and individuals, so that additional administrative procedures are essential in order to select from a strip information which will be both accurate and complete. These latter procedures are relatively complex and in some cases result in errors.